1. Field of the Invention
The present invention relates, in general, to door locks and, more particularly, to a push-pull door lock allowing a door to be opened and closed by pushing or pulling a knob of the door.
2. Description of the Prior Art
As well known to those skilled in the art, a door having a conventional rotary door lock may be opened and closed by pushing or pulling a knob of the lock while the knob is rotated clockwise or counterclockwise.
FIGS. 10a and 10b are vertical sectional views, showing an operation of such a conventional rotary door lock. In the conventional rotary door lock, two knobs 81 are provided at the inside and outside of the door, and a spindle (not shown) is rotatably mounted between the knobs 81. A slider 83 is provided within the interior of the door so as to be slid by the projection 82 on the end of the spindle. A latch bolt 87 is connected to one side of the slider 83, with a bolt compression spring 88 being interposed between the latch bolt 87 and the slider 83. Two slider compression springs 86 are positioned between a case 85 and the other side of the slider 83 so that a restoring force of the slider compression springs 86 is exerted on the slider 83.
In a normal state, the latch bolt 87 is extended as shown in FIG. 10a and is inserted into the insertion recess of a doorframe (not shown), thereby keeping the door closed. When the door is desired to be opened, the knob 81 is rotated clockwise or counterclockwise, so that the projection 82 pushes the loop 84 of the slider 83, thereby removing the latch bolt 87 from the insertion recess. As shown in FIG. 10b, the door is opened by pushing or pulling the knob 81 while the latch bolt 87 is removed from the insertion recess. When the knob 81 is released, the slider 83 is returned to its original position by the restoring force of the slider compression springs 86.
However, according to the conventional rotary door lock, the following disadvantages occur.
Since such a door has to be opened while a knob of the door is rotated clockwise or counterclockwise, it is difficult for a medical patient, a child and a user with his both hands occupied to open the door. Since noise occurs while the knob is rotated, it is difficult to use the door lock in such a place in which silence is required. Additionally, since the projection of a spindle and the loop of a slider are worn out by friction between them, the door lock has a short life span.